Pick and place machines are known in the art, examples of which are shown in the patents to Tamai et al, U.S. Pat. No. 4,381,601, Araki et al, U.S. Pat. No. 4,327,482, and Snyder et al, U.S. Pat. No. 4,135,630, the disclosures of which are hereby incorporated by reference. Such machines are designed generally to detachably attach an electronic component to a pick and place head at a first location, a supply station, carry the electronic component to a precisely defined second location, a work location, and place the electronic component onto a precisely defined position on a workpiece at the second location. Typically, these pick and place machines employ a vacuum head which attaches the electronic component to the pick and place head as the result of a vacuum suction, which is released when the pick and place head is moved to the second location. In addition, the pick and place heads are typically mounted for reciprocal motion in a direction perpendicular to the X, Y positioning plane, in order to both move the head downwardly at the first location, to attach the electronic component to the head, and to move the head downwardly at the second location, to place the component part adjacent the workpiece, and then press the component part downward onto the workpiece. The electronic components are typically computer chips and like circuit board components, with the workpiece typically being a circuit board, and the function of the head pressing the component down onto the workpiece must be done with the leads of the electronic component, if any, aligned with mating holes in the printed circuit board. Even if there are no leads, typically, components must be placed to be oriented in a specific way on the circuit boards.
It is thus crucial that the pick and place machine not only be properly controlled to select a proper part from a proper location and transport that part to the proper second location, but also that the part be correctly aligned on the pick and place machine head, such that at the second location, e.g., the electrical leads of the part will be properly aligned with the associated mating holes in the printed circuit board.
The above mentioned patents show centering jaws for accomplishing this general purpose. However, each of the centering jaw arrangements shown in the above noted patents involve centering jaws which require a large amount of vertical space and are formed on the foot of a pivoted member which is pivoted about a point axially displaced from the pivoting jaws in a direction aligned with the axis of reciprocal motion of the pick and place head, and with the pivot axis aligned with the X, Y plane. Thus, for example, in the patent to Tamai et al (referred to above) in FIGS. 5a, b and c, the jaws 33 are shown to pivot about pivot pins 32 through a lever action on rollers 40 created by a cam 41, with the pivot pins 32 displaced above the pick and place head 2 and the rollers displaced further above the pivot pins 32. In like manner, FIGS. 10, 11, 13 and 14 of the patent to Araki et al (referred to above) show the jaws 25, 25' and 24, 24' pivoted about pivot points 22, 22' and 23, 23' displaced above the pick and place head 2 and brought into engagement by the action of springs 26, 27 disposed intermediate the pivot points and the jaws and also axially above the jaws in the direction perpendicular to the X, Y plane. Similarly also, the patent to Synder et al (referred to above) in, for example, FIGS. 7, 8 and 11 shows the jaws 326 pivoting about knife blade pivots 301 contained in grooves 300 disposed above the pick and place head 2, with the axis of pivoting parallel to the X, Y plane.
Such arrangements of the aligning jaws create several problems. First, because the jaws in such an arrangement swing in an arc and not parallel to the X, Y plane, the flat surfaces of the jaws which engage the part to align the part on the pick and place head are vertically oriented only for a particular component part size equal to the distance between the engaging flat surfaces of the jaws when those flat surfaces are in alignment with the axial direction of the reciprocal motion of the pick and place head. If the component part is either too large or too small, when the jaws engage the component part, the flat surfaces of the jaws will be out of alignment with the axial direction of reciprocal motion of the pick and place head. This may cause the component part to be canted or twisted out of alignment with a plane parallel to the X, Y plane.
This creates two problems at the point of attachment of the electronic component part to the pick and place head. First, the component may be damaged due to stresses placed on the component because the direction of force applied to the component is not aligned with the plane of the component. Second, the component may be twisted sufficiently from the plane perpendicular to the axial direction of reciprocal motion of the pick and place head sufficiently to break the vacuum which holds the component to the pick and place head. This may cause the component to become further unaligned from the direction of force application by the flat engaging surfaces of the alignment jaws, particularly in the case of force application by spring means, as shown in the patent to Araki et al. However, even where the force application is regulated, the misalignment of the component part may cause the application of a regulated torque to be sufficient to damage the component due to its misorientation.
A further problem results when the canted or twisted component part misaligned with the direction of the plane perpendicular to the axial direction of reciprocal motion of the pick and place head is attempted to be placed upon a workpiece at a second location by the pick and place machine. As mentioned above, the electrical components typically have electrical leads which must be placed in corresponding holes in, for example, a circuit board. If the component part is misaligned with the plane perpendicular to the axial direction of reciprocal motion of the pick and place head, the leads very likely will not properly mate with the corresponding holes on the circuit board. Thus, when the pick and place head presses the component down to the circuit board, the electrical leads most likely will not all fit into their associated holes in the circuit board, and, further, the leads may be bent or even broken as a result of the application of the pushing force in the direction of the reciprocal motion of the pick and place head during the placing operation.
The above-noted problems with the prior art are not intended to be exhaustive, but rather are give as examples of the disadvantages of presently existing alignment jaws employed with pick and place machines.
Recognizing the need for an improved alignment jaw arrangement for a pick and place machine head, it is a general feature of the present invention to provide an improved alignment jaw arrangement for a pick and place head that is more compact vertically.
Another feature of the present invention is the provision of a linkage means associated with each jaw member of a respective pair of jaw members pivotally connected to a pivot point having a pivoting axis generally perpendicular to the head plate.
Yet still another feature of the present invention is the provision of jaw operating means for simultaneously pivoting the linkage means for each jaw of a respective pair of jaws about the respective linkage means pivotal connection.
A further feature of the present invention is to provide the jaw members of the first pair of jaws with a relatively broader component part engaging surface and the jaw members of the second pair with a relatively narrower component part engaging surface.
Still a further feature of the present invention comprises the jaw operating means including first and second internally threaded nuts pivotally connected to a respective one of the linkage means for a respective pair of jaw members and a threaded shaft threadedly engaging the first and second internally threaded nuts, with the shaft and nuts threaded such that rotation of the shaft in one direction moves the threaded nuts towards each other and rotation of the shaft in the other direction moves the nuts away from each other.
Still another further feature of the present invention involves the combination in a pick and place machine of a head body, means for mounting the head body for motion between a first postion from which a part is to be taken and a second position to which a part is to be transferred, a chuck mounted to the head body for reciprocating motion in a first direction toward and away from the device carrying the part to be taken at the first position and a workpiece at the second position, with the chuck having a tip including means for detachably securing a part to the tip and means for shifting the component part secured to the tip comprising a shaft plate with an aperture for receiving the chuck and disposed in a plane substantially perpendicular to the first direction and having first and second pairs of opposed centering jaws slidably mounted to the shift plate for motion substantially parallel to the plane of the shift plate toward and away from the aperture.
Yet still another further feature of the present invention is the provision of a lost motion pivotal connection between the respective linkage for each respective jaw of each of the pair of jaws, with the lost motion pivotal linkage comprising a lost motion slot generally aligned with the longitudinal axis of the respective linkage in the vicinity adjacent the jaw.
Still another and yet further feature of the present invention is the pivotal connection of the linkages for each jaw of a respective pair of jaws at an end of the linkages remote from the end connected to the respective jaw.
The above noted features and advantages of the present invention are not intended to be exhaustive, but rather are illustrative of the features and advantages of the present invention and are offered in order that those skilled in the art may better understand the present invention and the contribution to the art. These and other advantages and features of the present invention will be better understood by reference to the Detailed Description of a Preferred Embodiment referred to below in connection with the drawings, in the figures of which like reference numerals have been used to identify like elements.